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October 18, 2006

New theory explains enhanced superconductivity in nanowires

This could lead to better utilization of superconducting wires and the ability to get enhanced superconducting characteristics.

From physorg.com, Superconducting wires are used in magnetic resonance imaging machines, high-speed magnetic-levitation trains, and in sensitive devices that detect variations in the magnetic field of a brain. Eventually, ultra-narrow superconducting wires might be used in power lines designed to carry electrical energy long distances with little loss.

Researchers at the University of Illinois at Urbana-Champaign not only have discovered an unusual phenomenon in which ultra-narrow wires show enhanced superconductivity when exposed to strong magnetic fields, they also have developed a theory to explain it.

Magnetic fields are generally observed to suppress a material's ability to exhibit superconductivity – the ability of materials to carry electrical current without any resistance at low enough temperatures. Deviations from this convention have been observed, but there is no commonly accepted explanation for these exceptions, although several ideas have been proposed.

Magnetic fields can enhance the critical current in superconducting wires with very small diameters.

With postdoctoral research associate Andrey Rogachev (now a physics professor at the University of Utah) and graduate student Anthony Bollinger, Bezryadin deposited either niobium or an alloy of molybdenum and germanium onto carbon nanotubes to fabricate wires that were less than 10 nanometers wide. The superconductivity of these wires under a range of applied magnetic fields was examined, and the experimental results were compared with the proposed theory, revealing an excellent correlation between the two.

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